Caption: False-colour scanning electron micrograph of Vermiculite, or Micafill, showing its laminated structure. This material is sold for insulating purposes (in roof spaces for example). It consists of expanded mica. Mica is a mineral composed of aluminium silicate together with sodium, magnesium and potassium silicates. Its salient characteristic is its perfect basal cleavage, which means that it can be separated into very thin laminae. It is non-flammable, and because the expansion process introduces air between the layers it is light, and a good insulator. Magnification: x18 at 6x7cm size.